<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.js"></script>
    <style>
        .search{
            position: relative;
            width: 178px;
            margin: 100px;
        }
        .con{
            width: 178px;
            position: absolute;
            top: -40px;
            left: 1px;
            border: 1px solid rgba(0, 0,0,.2);
            box-shadow: 0 2px 4px rgba(0, 0,0,.2);
            padding: 5px 0;
            font-size: 18px;
            line-height: 20px;
            color: #333;
            display: none;
        }
        .con::before{
            content: "";
            width:0;
            height: 0;
            position: absolute;
            top: 28px;
            left: 18px;
            border: 8px solid black;
            border-style: solid dashed dashed;
            border-color: #fff transparent transparent;
        }
    </style>
</head>
<body>
    <div class="search">
        <div class="con">123</div>
        <input type="text" placeholder="请输入您的快递单号" class="jd">

    </div>
    <script>
        // var con = $(".con");
        // console.log(con)
        // $(".jd").keyup(function(){
        //     if(this.value == '')
        //     {   
        //         console.log(this.value)
        //         // con.style.display = 'none';
        //     }
        //     else{
        //         // con.style.display = "block";
        //         con.innerHTML = this.value;
        //     }

        // })
        // // $(".jd")
        var con = document.querySelector('.con');
        var jd_input = document.querySelector('.jd');
        jd_input.addEventListener('keyup',function(){
            if(this.value==''){
                con.style.display = 'none'
            }
            else{
                con.style.display = 'block'
                con.innerHTML = this.value;
                
            }
           
        })
        jd_input.addEventListener('blur',function(){
            con.style.display = 'none'
        })
        jd_input.addEventListener('focus',function(){
            if(this.value!=''){
                con.style.display = 'block'
            }
        })
    </script>
</body>
</html>